Vacuum condenser



R. H. CHAMBERLIN ETAL 2,533,713

Dec. z, 1950 VACUUM CONDENSER 2 Sheets-Sheet 1 Filed May 27, 1947INVENTOR Richard h'. Chamber/'n BY Harold E. So/'9 ATTOENEY PatentedDec. 12, 1950 UNITED STATES PATENT OFFICE VACUUM CONDENSER Richard H.Chamberlin, San Bruno, and Harold E. Sorg, Redwood City, Calif.,assignors to Eitel-McCullough, Inc., San Bruno, Calif., a corporation ofCalifornia Application May 27, 1947, Serial No. '750,828

1 Claim.

Our invention relates to condensers for use in electrical crcuts, andmore particularly to a condenser in which the electrodes are enclosed inan evacuated envelope.

Vacuum condensers as made in the past present a number of problems bothfrom the standpoint of the manufacture and of electrical design. Sincethe capacitance is determined by spacing between the electrodes, whichSpacing is necessarily quite close, there is a real problem of gettingthe electrodes sealed into an envelope while maintaining the properspacing between the electrodes. consequently, precision vacuumcondensers have seldom been available except at large cost. I he usualpractice has been to employ electrodes in the shane of parallel platesor concentric cylinders, the latter being commonly used. These electrodestructures are difficult to fabricate and assemble, and requireenvelopes of relatively large size for condensers in the highercapacitance ranges. Vacuum #condensers heretofore' made are also quitelimited in their current ratings because of heat` problems involved, andleave much to be desired mechanically.

The broad object of our invention is to provide an improved vacuumcondenser structure and fabrication method which largely overcomes thedisadvantages above noted.

The invention possesses other objects and features of advantage, some ofwhich, with the fore-.

going, will be set forth in the following description of our invention.It is tobe understood that we do" not limit ourselves to this disclosureof species of our invention as we may adopt variant embodiments thereofwithin the scope of the claim. i

Referring to the drawings:

Figure 1 is a longitudinal sectional View of a vacuum condenserembodying the improvements of our invention.

Figure 2 is a transverse sectional view taken in a plane indicated byline 2-2 of Fgure 1; and

Figures 3 and 4 are like views illustrating modied electrodes.

Figure' is a View similar to Figure 1 showing a condenser embodyingmeans for establishing the final capacitance; and

Figure 6 is another similar View illustrating the method of assembly.

Figure 7 is a detail View showing analternate closure structure. v

In terms of broad inclusion, our preferred condenser structure comprisesan evacuated envelope containing sets of electrodes, one electrode sethaving a plurality of parallel bores and the i other set having pinsprojecting into the bores. Theelectrode sets are preferably supported atopposite ends of the envelope and the set having the bores is preferablyformed by a group of tubes arranged side-by-side. The above structure issimple to fabricate and assemble, and permits building up a large capacitance in a compact space. An important feature of our invention isthe provision of adjusting means accessible externally of the envelopefor varying the spacing between electrodes to establish the finalcapacitance after the electrodes have been sealed in the envelope, meansbeing also provided for sealing the adjusting means to provide a vacuumtight closure after the adjustment has been made. While this feature maybe incorporatecl in vacuum condensers having other types of electrodes,our preferred electrode structure is particularly well suited becauseone of the electrode pins may easily be made adjustable to function as atrimmer electrode. Our method of making the condenser comprisespositioning the electrode sets to approximate the final capacitance,sealing the sets sopositioned in the envelope, varying the spacing byadjusting the trimmer electrode, fixing the spacing, and then evacuatingthe envelope. The method also preferably includes the step of placing adissolvable material between the electrodes to temporarily hold theelectrode sets as a unit while being sealed into the envelope, whichmaterial is subsequently dissolved out prior to final adjustment andevacuation,

In greater detail, and referring first to Figures 1 and 2 of thedrawing, one version of our vacuum condenser structure 'comprises atubular or cylindr cal envelope having a side wall 2 of a vitreousinsulating material such as glass or ceramic. End walls 3 of theenvelope are preferably of metal selected for making suitable joints tothe vitreous wall 2. For example, if the side wall is of glass, the endwalls are in the nature of sealing flanges and are made of a metalhaving an expansio characteristic matching that of the glass so that theparts may be sealed together at seals 4.

Internally our condenser comprises a pair of cooperating sets ofelectrodes positioned axially of the envelope and generally indicated bythe reference numerals 5 and l. Electrode set 6 simply comprises a solidbody 5 of metal such as copper having parallel bores 8 disposed aboutthe envelope azis and opening out on the inner end of body 5. Thesebores provide a plurality of individual hollow electrodes and arepreferably arranged in concentric circles about the 'in Figure isenvelope axis. An integral shank portion 9 extends through the end ofthe envelope to provide a terminal iii for the condenser. The outerterminal portion of the shank is preferably held in a cap li which is inturn secured to the end wall ange at braze !2.

` The other electrode l comprises a plurality of pins !3 projecting intoheres These free encled pin-shaped eleotrodes are seoured at their baseends to a shank i i which extends through the other end of the envelopeto provide a. second terminal i for the condenser. The shank at this endof the condenser has a cap !i secured to wall flange 3 in a mannersimilar to the construction at the opposite end. Pins !3 and mountingshani: !li of eiectrode set 'n' are of a suitable metal such as Copper.A metal exhaust tubulation is is preferahly brazed to terminal ID andported into the envelope through channel ll, the tubulation beingpinched ofi at tip ae after evacuaton of the envelope.

The capacitance of our condenser is deter.- minecl by the number anddimensions of bores 3 and engagecl pins ecause multiplicity ofinterengaged electrodes present a large total area in a compactstructure, it is possible to build oondensers of large capacitance inenvelopes of small physical size. Another feature of our Construction isthat the relatively large mass of metal connecting the effectiveelectrode areas with the terminals provides excellent hoat conduction sothat the improved condenser, even though of small size, is capable ofhandling large Currents without urdue heating.

Other advantages of our condenser structure above described include thefollowing: There are but few parts and that are` present are readilyfabricated assembled; the electro-;les are easily *d for aiignmc whenseaiing into the enveiope and have ample ribidity to maintain accuratealignrnent even though small interelectrode spaoiogs are involved; therigidity above mentioned holds the capacitanoe constant under eleotrioalstresses; the condenser is ideally adapted for soale production on aneconomioal hasis; and the simple st *ure does not introduce problems inoutgassing of parte and evacuation of 'the envelope during exhaust ofthe condenser.

11155634921 of making the electro-;le set 6 of a solid block of metal,:it can cellular structure made up of a group of metal tuhes iiiarranged side-hy-side as shown in 3, which tubes are preferahly ofcopper hrazed together and to a mounting shanit. The tuhes may hoircular as in Figure 3 or flat sided Figure 4. Hexagonai` tuhes ho tedtogether build up a very large capacitanoe all particularly the are alsoh onaL Since the cellular structure has from thefahrication standpointwell providing further compactness, we prefer to use it.

Another .feature of our invention illustrated the provision of adjustingaccessible externally of envelope for va'ying the spaoing hetwe nelectrodes to estahlish the final capaoitance after the eiectrodes haveheen sealed in the envelope. As emhodied in our pin type electrode'structure this adjusting feature utilzing the center pin ti of elec rodeset i as a trimmer eleotrode. Ali of the ot electrcdes, which. are fixedat the time of them into the en'velope, will be referred to heroin asthe main electrocles to distinguish them from the trimmer electrodeTrimmer eleotrode i has an outer screw portion threaded into a passage22 extending through shank i and exposed at the end of the condenser, sothat the outer screw portion provides means for adjustng the electrode.A screwdriver inserted in the passage is the only tool required to makethe final adjustment. After adiustment and prior to evacuation the outerendof passage 22 is sealed with a fused metallio plug 23 of solder orthe like. This plug provides a vacuum tight closure and alsosimultaneously locks the trimmer electrode to fiX the spacing.

While we have shown the above feature in connection with our preferredpin type electrode structure, it is understood that it may beincorporated in any type of vacuum condenser where it is desired to makean adjustment for trimming the capacitance to a precise Value prior toevacuating the envelope,

Summarizing the method of making the condenser, and referring to F'igu'e6, we first fabrieate'theeleotrode sets 6 and 'i and then engage themain electrodes and trimmer electrode to approximate the finalcapacitance. This positioning may be done with suitable jigs orfixtures. The electrode sets so positioned are then sealed in theenvelope by fusing the vitreous side wall 2 to metal end walls sat seals4. This sealing operation serves to fix the main electrodes in`permanent position will be readily understood. Since the finalcapacitance is not set during the sealing-in operation enough tolerancesare allowable to permit the glass work to be done without unduerestrictions. Seals 4 are made in an ordinary lass lathe.`

The next step is to trim the. capacitance by movingl electrode 2| in orout. This is preferably done withthe condenser in a capacitancemeasuring circuit. After adjustment a quantity of solder is poured intopassage 22 to form the plug 23 (Figure 5), thereby locking the trimmerelectrode and providing a vacuum tight closure for the adjusting means.The condenser is then ready for evacuation which is done in theconventional manner by connectin tubulation IE to a suitable vacuumpump.

If desired an additional step may be employed to simplify holding theelectrode sets 6 and 'I as a unit during the sealing-in operation. Thiscomprises filling several of the bores with a dissolvable material 26such as salt or chalk to embed the engaged ;pins [3. After the envelopehas been completed the material 25 is dissolved out by introducing asuitable liquid solvent through the open tubulation [6. The steps oftrimming adjustment and evacuation may then be followed as previouslydescribed; Using a dissolvable material to hold the electrodes has aspecial advantage in making the Simpler form of structure shown inFigure 1, although the. combination of this step with a subsequent`trimming adjustment is an ideal method of making preoision condensers.Our pin type electrode structure is particularly well adapted for use ofthe dissolvable spacing material 25 because the only cavitics are thebores &which all face in one direction, thereby making it easy to washout the spacing material.

A modified structure for looking the trimmer electrode andsimultaneously providing a vacuum tight closure is shown in Figure 7,wherein` an extension rod 21 on electrode 2| projects through a metaltubulation 28; both of which are pinched off at tip 29. By thisarrangement the extension 21; which is Originally made long enoughtoproject out the open end of tubulation, provides a handle for adjustingthe trimmer electrode. The subsequent step of pinching through the partsserves to lock them together as well as to seal ofi' this end of thecondenser. This tubulated structure on an envelope, with a rod extendingthrough the tubulation for adjusting the position of an element withinthe envelope, is useful in any kind of evacuated device Where it isdesirable to make a final adjustment prior to sealing the envelope.

We claim:

A vacuum condenser comprising an envelope having an end structure with apassage therein, an electrode' set supported at the opposte end of theenvelope and. having parallel bores, another electrode set supported atthe first mentioned end of the envelope and having pins projecting intosaid bores, adjusting means threaded into` said passage for varying thedegree of engagement of one of said pins, and a vacuum tight closure forthe outer end of the passage.

RICHARD H. CHAMBERLIN. HAROLD E. SORG.

REFERENCES CITD The following references are of record in the file ofthis patent:

UNITED STATS PATENTS Number Name Date 1,333,401 Fisk Mar. 9, 19201,641,687 Nolte Sept. 6, 1927 2,036,532 Knoll Apr. 7, 1936 2,154,542Swanson Apr. 18, 1939 2,192,062 Hansell Feb. 27, 1940 2,291,445 BeyerJuly 28, 1942 2,324,178 Sprague July 13, 1943 2,339,663 Teare Jan. 18,1944 2,415,412 Bushwald Feb. 11, 1947 FOREIGN PATENTS Number CountryDate 416,157 Great Britain Sept. 14, 1934 523,869 Great Britain July 24,1940

